A 400kg (880pounds) machine part fell into a nuclear fuel pool at Japan’s crippled Fukushima plant on Friday, the operator said.
Friday’s incident occurred shortly after noon during a remotely controlled operation to remove debris from the fuel pool at the unit where the broken reactor still lies untouched.
The operating console of the fuel-handling machine slipped loose and fell into the pool as it was about to be lifted by a crane, TEPCO said in a statement.
The console weighed 400kg and measured 160cm by 90cm by 100cm (roughly 5 feet by 3 feet by 3 feet,) a TEPCO official said.
The Independed also noted:
The pool contains 566 fuel rods, most of which are spent.
This causes me to worry about accidental criticality. Under normal circumstances, both new and spent fuel rods are subject to spacing requirements. Fissionable materials cannot be too close to each other, as they are subject to criticality, that is, compacted nuclear material can cause enough interaction that a chain reaction can occur, and a sustained chain reaction can cause nuclear materials to melt.
Dropping a huge mass of metal into a pool where fuel rods lie like Pixie Sticks can crush or dislodge the fuel rods, resulting in placing rods in closer proximity than is safe. Fortunately, it does not appear that there is any measurable increase in radioactivity in the fuel pool.
One other item in the Independent report that I find a little puzzling:
The Tokyo Electric Power Company (TEPCO), said it had not detected any significant changes … in the level of pool water at the No. 3 reactor.
This seems to me to violate the laws of physics. 880 pounds of steel dropped into a swimming pool should displace 880 pounds of water, assuming that steel doesn’t float in water. (Kind of a Monty Python reference.) If the water level doesn’t rise, where did the water go?
And the Independent mentions a fact that indicates that the forces that caused the Fukushima disaster are still present:
In a vivid reminder of the fragility of the area, a magnitude-5.0 quake struck off the Fukushima coast hours after Friday’s incident.